Re: 1988 100hp merc ignition coils
That depends. It should not harm the cd if the spark plug is grounded, or say, the plug wire is arcing to ground. But if a plug fouls, a plug wire falls off, leaving no destination for the pulse to go, yes, it could 'find' the nearest ground. This could be thru the dialectric compound poured around the coil to the frame of the motor, which could damage it.<br />Old tv sets used to suffer early deaths sometimes, due to dust giving a conductive path accross an area that was not where it was to go. As soon as an arc occured, the path it took, would have a nice path made of carbon (conductive) from the HV output to ground.<br />You may have heard this in a tv that got wet. a snapping would be heard, or a sound like water on a hot pan.<br />Your manual will warn "not to disconnect a plug wire and allow the motor to run, as damage to the HVCD unit may occur".<br />A bad plug wire, or arcing could make an engine run poorly tho for sure, and also allow the plug to foul,and then the poor path to ground can ruin stuff.